Incidence among children is on the rise
Due to the increasing incidence of peanut allergies, especially in young children, the diagnosis and management of these allergies is a pressing national concern. Peanut allergies are the most common cause of food allergy-related deaths, accounting for 55% in the United States.1,2
A cross-sectional study found that the number of self-reported cases of peanut allergy in children has tripled between 1997 and 2008.3 With an increasing number of children bearing the potential for hypersensitivity reactions, the topic of peanut allergy has become a public health concern that many are eager to understand.
Overall, the area of peanut allergies is still being explored and research is ongoing to help improve our understanding and management of peanut allergies. This article focuses on the epidemiology, pathophysiology, manifestations, diagnosis and potential treatment options of peanut allergy among children.
Commonly arising in childhood and persisting lifelong, peanut allergies are an IgE-mediated type I hypersensitivity reaction and can cause reactions ranging from mild skin irritation to fatal anaphylactic shock.
Although some studies have shown that up to 20% of peanut allergies in children may resolve spontaneously, peanut allergies may recur, even in patients who have had negative oral challenges. In one study, 8% of children diagnosed with peanut allergy who later became tolerant, as indicated by negative challenge, could not, in the future, tolerate peanuts in their diet.5
Recent evidence shows that the development of peanut allergy may have a genetic component. A child with a parent or sibling with peanut allergy has a seven-fold increased chance of developing the allergy. A study of monozygotic twins found a 64% likelihood of a child having a peanut allergy if his/her monozygotic twin had the same allergy.6
Children may have adverse reactions to peanuts, which may or may not be immunological in nature. Determining if the reaction is immunological is key to the diagnosis of peanut allergies.
Immunological reactions are considered an “adverse health effect arising from a specific immune response that occurs reproducibly on exposure to a given food.” 6 In susceptible people, peanut proteins cause an IgE-mediated type I hypersensitivity reaction. Exposure to the peanut protein allergen leads to the production of allergen specific IgE, which is then bound to high-affinity IgE receptors on mast cells or basophils.
During this phase, after the initial exposure, the patient remains asymptomatic. However, the patient becomes vulnerable to an allergic reaction in the event of subsequent re-exposure to the allergen. At that point, there is cross-linkage between the peanut allergen and the cell-bound IgE that results in degranulation of preformed inflammatory mediators like histamine, prostaglandins and leukotrienes.
The cells also produce interleukin (IL)-4 and IL-13, cytokines, and chemokines, which results in the recruitment of other inflammatory cells. Allergic symptoms and anaphylaxis are the result of the chemical reactions that occur.4
An allergic reaction to peanuts can present in a multitude of ways, ranging from a mild reaction to fatal anaphylactic shock. These reactions develop rapidly upon exposure to the allergen and are notorious for their severity.
In a study of children who were allergic to (either is only used to compare two things; people commonly use it incorrectly!) milk, eggs or peanuts, hypersensitivity reactions to peanuts were the most severe. Severe reactions were reported in 20.4% of children, while similar reactions in response to milk and eggs were reported as 9.1% and 11.4%, respectively. Citation?
These results are supported in another study showing that peanut allergen is disproportionately implicated as a trigger of severe reactions among those who are affected. The humoral immune response to peanut allergens in susceptible patients is more strongly IgE biased compared to the immune response to milk allergens, against which atopic patients tend to make both IgE and IgG.7
Hypersensitivity reactions to peanuts commonly involve multiple organ systems, resulting in varied presentation. A reaction can present with cutaneous, respiratory, gastrointestinal, ocular and/or nasal manifestations. A cutaneous eruption often involves the skin or mucus membranes, and includes erythema, hives, pruritus and/or edema.6 Respiratory manifestations are often present and can be severe, presenting with chest tightness, wheezing, coughing and intercostal retractions. Asthma and allergic rhinitis can also be exacerbated by this allergy, but are not true manifestations of the peanut allergy itself.6
Gastrointestinal characteristics include vomiting, diarrhea and abdominal discomfort. Nasal manifestations can appear as rhinorrhea, sneezing or nasal pruritus, and ocular manifestations occur as conjunctival erythema, tearing and pruritus.
Anaphylaxis, the most severe reaction, can occur within seconds to minutes of peanut exposure or ingestion. This type of reaction can lead to massive vasodilation, decreased organ perfusion and death. Anaphylactic shock can affect multiple organ systems, including cardiovascular, gastrointestinal, ocular, nasal, respiratory, cutaneous and neurologic function. The reaction can be fatal, and requires immediate intervention.
Hypersensitivity reactions can present in various combinations and can be manifested differently from patient to patient.2,4
The first step in the diagnosis of a peanut allergy is to identify the peanut as the cause of the allergic reaction. This can be accomplished through a detailed history and physical exam.
The next step is detection of peanut-specific IgE by skin prick test or in vitro assays. Skin prick tests are performed with commercially available peanut extract and are a convenient, inexpensive and rapidly interpretable test. They are also a safe test, with serious adverse effects being extremely rare and no reported fatalities.
Alternately, in vitro testing is available through a variety of assays, and can be useful in patients who cannot stop taking antihistamines, which is required prior to skin testing. However, they are more expensive, results are delayed and the results must be processed through an approved laboratory.
Finally, the gold standard for confirming a peanut allergy is a double-blind, placebo-controlled peanut food challenge in which the patient ingests incremental portions of peanut proteins or placebo at 15- to 30-minute intervals with documentation of signs and symptoms prior to each dose. The challenge is stopped and treatment is provided immediately if a reaction develops. This test is definitive; however, it is time consuming, requires close medical supervision and carries the risk of a severe allergic reaction.4
No cure for peanut allergy has been developed. Therefore, strict avoidance and preparedness for accidental exposure is the cornerstone of management.1,6
Primary management involves allergen avoidance to prevent the development of hypersensitivity reactions and the availability of self-injectable epinephrine for treatment of severe reactions secondary to accidental exposure.2 There are differing opinions about whether children with peanut allergies should be advised to remove all nuts from their diets, irrespective of allergy testing results, in order to avoid accidental cross-contamination and/or the possibility of developing new allergies.
In a study by Ball et al, none of the patients with negative skin test results reacted on oral tree nut challenge. Alternately, about 31% of patients with positive skin tests to tree nuts reacted on oral challenge with tree nuts. The study results suggest that children who are allergic to peanuts and have negative allergy tests to tree nuts may have no co-existing allergy.8 In patients with positive skin tests to tree nuts, oral challenges may clarify the actual clinical allergy status and reduce anxiety and minimize dietary restrictions. Because the diagnosis of food allergies can impose significant psychological burdens on children and their families, rather than increasing restriction, patients should be well educated on the specifics of their diagnosis and necessary management.8
The second area of peanut allergy management is the treatment of acute IgE-mediated reactions due accidental exposure. The amount of peanut protein necessary to cause an allergic reaction may be small. Cross-contamination of food and trace amounts of peanut proteins make strict peanut avoidance extremely difficult.1 For children with peanut allergy, the annual incidence rate of accidental exposure is 12.5%. Adolescents and children with more recent diagnosis are at the greatest risk. Many accidental exposures occur in patients’ homes and in peanut-free facilities, indicating the importance of vigilance, even in environments that are considered “safe” and controlled.1
Children with peanut allergies and their families should also be taught to recognize the early signs of an allergic reaction.4 Additionally, they should be educated about carrying and properly administering self-injectable epinephrine.
Early injection of epinephrine decreases the risk of fatal outcomes and biphasic reactions, which can occur 1 to 8 hours after the onset of symptoms.4 Anaphylactic reactions should be treated immediately with intramuscular epinephrine injected into the mid-outer aspect of the thigh, and then transported to a medical facility for further treatment.2 Upon arrival, the patient should be placed in the supine position with the lower extremities elevated. If the patient is dyspneic or vomiting, he or she should be placed in the semi-recumbent position with lower extremities elevated. Supplemental oxygen via facemask should be provided, as well as volume resuscitation with intravenous fluids.9 Systemic corticosteroids and antihistamines can be used, as needed.
Up to 30% of anaphylactic reactions have a biphasic course, so patients should be observed for 4 to 8 hours after the initial onset of symptoms. Along with a prescription for a renewed epinephrine auto injector, it is customary for patients to be given a 3-day course of oral prednisone and an antihistamine after they are treated and discharged.4
The potential for a curative treatment option for peanut allergies is being researched. Oral immunotherapy is under investigation, but not currently approved.1
Oral and traditional injection immunotherapy are not favored for peanut allergy because of a high incidence of serious side effects though there have been a few documented cases of successfully achieved tolerance as a result of these therapies, the high rate of adverse reactions make oral and injection therapy unacceptable for routine clinical use.4
A Cochrane review by Nurmatov et al found one small randomized clinical trial that showed desensitization was achieved in children who underwent oral immunotherapy. At the same time, a significant risk of adverse effects exists, although the majority were mild. Due to adverse effects and the lack of evidence supporting long-term benefits, allergen-specific oral immunotherapy cannot be recommended as a treatment for management of patients with IgE-mediated peanut allergy.10
This will remain true until larger trials are conducted to investigate the acceptability, long-term effectiveness and cost-effectiveness of safer treatment regimens.10
Patient & Caregiver Education
The thought of a fatal anaphylactic reaction is frightening to children and their parents and can cause severe worry and anxiety. To ease these fears and ensure the safety of children with allergies, education is imperative.
Furthermore, in attempt to ease worry and maintain a safe environment for children with peanut allergy, many schools, day camps and childcare institutions are declaring themselves “peanut free.”
Patients, parents and childcare workers need to be educated about reading food labels and asking about ingredients that may contain traces of peanut proteins.1 Education should include visual identification of peanuts and tree nuts, as well.11 Recognizing and avoiding food containing nuts is the key strategy to self-management of a peanut allergy.2
Additionally, patients should be counseled about accidental exposure due to trace amounts of nuts in “safe” foods and hidden ingredients in manufactured food that may contain nuts. It is imperative to educate patients and their caregivers immediately after diagnosis and during adolescence about how to best prevent an allergic reaction, since the greatest risk of accidental exposure is during those times.1
It is important for school personnel to be notified about a child’s allergy and to practice strict adherence to peanut-free environment policies. Furthermore, schools and childcare facilities should implement standard protocols to be followed in the event of an allergic reaction.
Depending on the severity of the patient’s allergy, it may be advisable for a child to wear a MedicAlert bracelet, which can alert others of the allergy in the event of an emergency.4 All personnel should also be educated on how to use injectable epinephrine.
Finally, even in institutions that consider themselves “peanut-free,” students and school personnel must remain cautious because many incidents of inadvertent exposure have been reported in such environments.1
1. Nguyen-Luu NU, et al. Inadvertent exposures in children with peanut allergy. Pediatr Allergy Immunol. 2012;23(2):133-9.
2. Barnett J, et al. Beyond labeling: what strategies do nut allergic individuals employ to make food choices? A qualitative study. PLoS One. 2013;8(1):e55293. doi: 10.1371/journal.pone.0055293.
3. Sicherer S, et al. U.S. prevalence of self-reported peanut, tree nut, and sesame allergy: 11-year Follow Up. J Allergy Clin Immunol. 2010;125(6):1322-6. doi:10.1016/jaci.2010.03.029
4. Husain Z, et al. Peanut allergy: an increasingly common life-threatening disorder. J Am Acad Dermatol. 2012;66(1):136-43. doi:10.1016/j.jaad.2011.02.031.
5. Hourihane JO. Peanut allergy. Pediatr Clin North Am. 2011;58(2):445-58, xi. doi: 10.1016/j.pcl.2011.02.004.
6. Mahoney E, et al. Food allergy in adults and children. Otolaryngol Clin North Am. 2011;44:816-833. doi:10.1016/j.otc.2011.03.014
7. Masilamani M, et al. Determinants of food allergy. Immunol Allergy Clin North Am. 2012; 32:11-33. doi:10.1016/j.iac.2011.12.003
8. Ball H, et al. Single nut or total nut avoidance in nut allergic children: outcome of nut challenges to guide exclusion diets. Pediatr Allergy Immunol. 2011; 22(8):808-12. doi: 10.1111/j.1399-3038.2011.01191.x.
9. Campbell, R, et al. Emergency department diagnosis and treatment of anaphylaxis: a practice parameter. Ann Allergy Asthma Immunol. 2014;113(6):599-608. doi: doi.org/10.1016/j.anal.2014.10.007
10. Nurmatov U, et al. Allergen-specific oral immunotherapy for peanut allergy. Cochrane Database Syst Rev. 2012;9:CD009014. doi: 10.1002/14651858.CD009014.pub2.
11. Hostetler TL, Hostetler SG, Phillips G, Martin BL. The ability of adults and children to visually identify peanuts and tree nuts. Ann Allergy Asthma Immunol. 2012;108(1):25-9. doi: 10.1016/j.anai.2011.09.012.